Patent document 1 describes an electronic device such as a mobile phone for transmitting the air conduction sound and bone conduction sound to the user. Patent document 1 also describes that the air conduction sound is sound transmitted to the auditory nerve of the user as vibration of the air caused by vibration of an object is transmitted to the eardrum through the ear canal and vibrates the eardrum. Patent document 1 further describes that the human body vibration sound is sound transmitted to the auditory nerve of the user through a part of the body (for example, the cartilage of the external ear) of the user in contact with a vibrating object.
Patent Document 1 describes a telephone equipment having a vibrator in a corrugated plate shape constituted by using a piezoelectric bimorph and a flexible substance attached to an external surface of a housing via an elastic member. Patent document 1 also describes that, when a voltage is applied on the piezoelectric bimorph of the vibrator, the vibrator vibrates in a curved manner as piezoelectric material expands and contracts in a longitudinal direction and the air conduction sound and the human body vibration sound are transmitted to the user when the user contacts the vibrator to the auricle.